As the use of low quality refinery feedstocks has increased, a concomitant need for improved hydroprocessing capacity has accompanied it as these feeds generally result in larger quantities of residual fractions in the refinery. At the same time, the long term needs to cut costs and to make cleaner products represent conflicting requirements. Feed accounts for about 70% of the refining and petrochemical costs therefore the use of less expensive feeds would cut costs. However, less expensive feeds typically have higher sulfur, metals, and aromatics which make them more costly to process. Thus, in order to meet the objective of reducing costs, the heavier crude oil fractions which contain the bulk of the sulfur, metals and aromatics must be processed more efficiently into the more valuable lower boiling fractions such as chemical feedstock.
One of the many types of processes developed for the treatment of residual feeds is the hydroconversion of heavy residual feedstocks in a slurry process using a catalyst prepared in a hydrocarbon oil from a thermally decomposable metal compound catalyst precursor. The catalyst may be formed in situ in the hydroconversion zone or separately as described, for example, in U.S. Pat. Nos. 4,134,825; 4,226,742; 4,244,839; 4,740,489 and 5,039,392 which describe processes of this type using catalysts based on the metals of Groups IVB, VB, VIIB, VIIB and VIII of the CAS Periodic Table (i.e., Groups 4-10 in the IUPAC Periodic Table (2004)), preferably from Groups VB, VIB and VIII (i.e., Groups 5, 6 and 8 through 10 in the IUPAC Periodic Table (2004)).
In the aforementioned process, it is possible to use hydrogen pressures which are far lower than the 1500-3000 psig (about 10,000-21,000 kPag) used in conventional hydroprocessing techniques. At these lower pressures, typically as low as 250 psig (about 1725 kPag), a substantial proportion, typically up to 65 wt. %, of 650° F.+ (345° C.+) resid molecules may be converted to lower boiling range products, e.g., 650° F.− (345° C.−) fractions, using a few hundred parts per million of a dispersed metal on carbon catalyst at 450° C. (about 840° F.). The small amount of catalyst is enough to maintain coke at a manageable level and the hydrogen pressure is low enough that aromatic rings are not saturated, so there is low hydrogen consumption. A significant portion of the feed is converted to lower boiling range products (e.g., products which may be treated as in the 650° F.− (345° C.−) boiling range) which are high in saturated (aliphatic) molecules. The higher boiling range portion of the reaction products (e.g., the 650° F.+ (345° C.+) portion) can then be treated in separate processing in a way which utilizes the favorable characteristics of the hydroconversion products.
While hydroprocessing is most efficient at moderate temperatures and high pressures, the cost of obtaining equipment that can withstand such extreme conditions is prohibitive. Likewise, the cost of associated hardware, such as compressors and heaters, necessary to achieve and maintain these operating parameters is high. Thus, it would be advantageous if a relatively simple and less expensive apparatus could be utilized to conduct hydroprocessing. The cost of producing higher purity hydrogen for use in conventional hydroprocessing is also high so processes which can utilize lower purity hydrogen are also of interest.
Pulse compression reactors are available as means of producing high temperature and high pressure environments for conducting reactions. U.S. Pat. Nos. 2,814,551 and 2,814,552, incorporated herein by reference, disclose improvements in the method of operating and in the construction of reciprocating compression reactors wherein a gas containing or believed to contain a reactant is compressed and promptly thereafter expanded, whereby the reactant is brought for a short time to a high temperature and high pressure. Such may be used to perform chemical reactions, such as cracking of hydrocarbons, synthesis reactions, etc.
“Pulsed Compression Technology: A Breakthrough in the Production of Hydrogen”, M. Glouchenkov and A. Kronberg, WHEC 16/Jun. 13-16, 2006, discloses a chemical reactor concept based on the principle of compressive heating and cooling, which permits a breakthrough in many chemical processes at high temperatures and pressures in terms of energy efficiency, capital costs and portability, using a pulsed compression reactor for production of hydrogen by noncatalytic partial oxidation of hydrocarbons. The reference suggests production of hydrogen-containing synthesis gas by feeding methane and oxygen to the pulsed compression reactor and reacting them under high temperature and pressure conditions of the reactor.